Genetic parameter estimation and gene association analyses for meat quality traits in open-air free-range Iberian pigs

Genome-wide runs of homozygosity signatures in diverse Indian goat breeds

The present study analyzed ROH and consensus ROH regions in 102 animals of eleven diverse Indian goat (Capra hircus) breeds using whole genome sequencing. A total of 51,705 ROH and 21,271 consensus regions were identified. The mean number of ROH per animal was highest in the meat breed, Jharkhand Black (2693) and lowest in the pashmina breed, Changthangi (60). The average length of ROH (ALROH) was maximum in Kanniadu (974.11 Kb) and minimum in Tellicherry (146.98 Kb). Long ROH is typically associated with more recent inbreeding, whereas short ROH is connected to more ancient inbreeding. The overall ROH-based genomic inbreeding (FROH) was highest for Jharkhand Black (0.602) followed by Kanniadu (0.120) and Sangamneri (0.108) among all breeds. FROH of Jharkhand Black was higher than Kanniadu  up to 5 Mb ROH length category. However, in > 20 Mb ROH length category, Kanniadu (0.98)  exhibited significantly higher FROH than Jharkhand Black (0.46). This  implies that Kanniadu had higher levels of recent inbreeding than Jharkhand Black. Despite this, due to the presence of both recent and ancient inbreeding, Jharkhand Black  demonstrated higher overall FROH compared to Kanniadu. ROH patterns revealed dual purpose (meat and dairy) and pashmina breeds as less consanguineous while recent inbreeding was apparent in meat breeds. Analysis of ROH consensus regions identified selection sweeps in key genes governing intramuscular fat deposition, meat tenderisation, lean meat production and carcass weight (CDK4, ALOX15, CASP9, PRDM16, DVL1) in meat breeds; milk fat percentage and mammary gland development (POLD1, NOTCH2, ARHGAP35) in dual purpose (meat and dairy) breeds; while cold adaptation and hair follicle development (APOBEC1, DNAJC3, F2RL1, FGF9) in pashmina breed. MAPK, RAS, BMP and Wnt signaling pathways associated with hair follicle morphogenesis in Changthangi were also identified. PCA analysis based on ROH consensus regions revealed that meat breeds are more diverse than other goat breeds/populations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03921-y.

Candidate SNPs for meat quality and carcass composition in free-range Iberian pigs

Several genetic markers, previously associated with meat quality traits, have been proposed to be included in Iberian pig breeding programs. However, before being implemented, effects of these candidate SNPs on premium cuts' yield should be evaluated to avoid potential undesirable antagonistic effects. Therefore, the main goals of this study were to evaluate the effects of a set of 26 polymorphisms on premium cuts weights and to corroborate their effects on meat quality in a larger population. Phenotypic data of approximately 1550 Iberian pigs were recorded. The PRKAG3_rs319678464C and PRKAG3_rs1108399077G alleles were associated with an increase of shear force, water losses and color values and a reduction of average daily gain (ADG). The CAST_rs196949783G > A and ADIPOQ_rs3476515794T > G SNPs mainly affected IMF content, with this last SNP being the only one with significant effects on any of the carcass measures, specifically Longissimus thoracis et lumborum (LTL) weight. The ELOVL6_rs3473714672A, FASN_rs331694510A, MTTP_rs335896411C and ACACA_rs340781986C alleles were linked to a higher percentage of oleic acid and monounsaturated FA and a decrease in palmitic, palmitoleic and saturated FA. Besides, suggestive effects were observed between ELOVL6_rs3473714672A > G and ham and shoulder weights, and between MTTP_rs335896411T > C and LTL muscle weight. Finally, the NR6A1_rs326780270T allele was associated with a significant increase in ADG and tended to reduce the ham weight. The SNPs mapped to PRKAG3 (rs319678464G > C), ACACA, FASN and CAST genes could be implemented in breeding programs to improve meat quality traits without undesirable effects on carcass composition. The SNPs mapped to PRKAG3 (rs1108399077G > A) ELOVL6, MTTP and NR6A1 should continue to be tested in a larger number of animals.

Expression profile of FASN gene and association of its polymorphisms with intramuscular fat content in Hu sheep

The content of intramuscular fat (IMF) is one of the most important factors that has a large impact on meat quality, and it is an effective way to improve IMF according to marker-assisted selection (MAS). Fatty-acid synthase (FASN) is a key gene in meat lipid deposition and fatty acid composition. Thus, this study was conducted to investigate the expression profile of FASN in mRNA and protein levels using real-time quantitative PCR (RT-qPCR) and western-blot methods. In addition, single nucleotide polymorphisms (SNPs) within FASN in 921 Hu rams with IMF content records were investigated using DNA-pooling sequencing and improved multiple ligase detection reaction (iMLDR) methods. Consequently, the highest mRNA expression level of FASN was observed in the perinephric fat, and the lowest in the liver among the 11 tissues analyzed, while no significant difference was found in mRNA and protein expression levels in longissimus dorsi among individuals with different IMF contents. A total of 10 putative SNPs were identified within FASN, and 9 of them can be genotyped by iMLDR method. Notably, two SNPs were significantly associated with IMF content, including NC_040262.1: g.5157 A > G in intron 5 (p = 0.046) and NC_040262.1: g.9413 T > C in intron 16 (p = 0.041), which supply molecular markers for improving meat quality in sheep breeding.

Identifying Genetic Architecture of Carcass and Meat Quality Traits in a Ningxiang Indigenous Pig Population

Ningxiang pig is a breed renowned for its exceptional meat quality, but it possesses suboptimal carcass traits. To elucidate the genetic architecture of meat quality and carcass traits in Ningxiang pigs, we assessed heritability and executed a genome-wide association study (GWAS) concerning carcass length, backfat thickness, meat color parameters (L.LD, a.LD, b.LD), and pH at two postmortem intervals (45 min and 24 h) within a Ningxiang pig population. Heritability estimates ranged from moderate to high (0.30~0.80) for carcass traits and from low to high (0.11~0.48) for meat quality traits. We identified 21 significant SNPs, the majority of which were situated within previously documented QTL regions. Furthermore, the GRM4 gene emerged as a pleiotropic gene that correlated with carcass length and backfat thickness. The ADGRF1, FKBP5, and PRIM2 genes were associated with carcass length, while the NIPBL gene was linked to backfat thickness. These genes hold the potential for use in selective breeding programs targeting carcass traits in Ningxiang pigs.

Genome-wide association study reveals genetic loci and candidate genes for meat quality traits in a four-way crossbred pig population

Meat quality traits (MQTs) have gained more attention from breeders due to their increasing economic value in the commercial pig industry. In this genome-wide association study (GWAS), 223 four-way intercross pigs were genotyped using the specific-locus amplified fragment sequencing (SLAF-seq) and phenotyped for PH at 45 min post mortem (PH45), meat color score (MC), marbling score (MA), water loss rate (WL), drip loss (DL) in the longissimus muscle, and cooking loss (CL) in the psoas major muscle. A total of 227, 921 filtered single nucleotide polymorphisms (SNPs) evenly distributed across the entire genome were detected to perform GWAS. A total of 64 SNPs were identified for six meat quality traits using the mixed linear model (MLM), of which 24 SNPs were located in previously reported QTL regions. The phenotypic variation explained (PVE) by the significant SNPs was from 2.43% to 16.32%. The genomic heritability estimates based on SNP for six meat-quality traits were low to moderate (0.07-0.47) being the lowest for CL and the highest for DL. A total of 30 genes located within 10 kb upstream or downstream of these significant SNPs were found. Furthermore, several candidate genes for MQTs were detected, including pH45 (GRM8), MC (ANKRD6), MA (MACROD2 and ABCG1), WL (TMEM50A), CL (PIP4K2A) and DL (CDYL2, CHL1, ABCA4, ZAG and SLC1A2). This study provided substantial new evidence for several candidate genes to participate in different pork quality traits. The identification of these SNPs and candidate genes provided a basis for molecular marker-assisted breeding and improvement of pork quality traits.

Combining genome-wide association study based on low-coverage whole genome sequencing and transcriptome analysis to reveal the key candidate genes affecting meat color in pigs

Meat color is an attractive trait that influences consumers' purchase decisions at the point of sale. To decipher the genetic basis of meat color traits, we performed a genome-wide association study based on low-coverage whole-genome sequencing. In total, 669 (Pietrain × Duroc) × (Landrace × Yorkshire) pigs were genotyped using low-coverage whole-genome sequencing. Single nucleotide polymorphism (SNP) calling and genotype imputation were performed using the BaseVar + STITCH channel. Six individuals with an average depth of 12.05× whole-genome resequencing were randomly selected to assess the accuracy of imputation. Heritability evaluation and genome-wide association study for meat color traits were conducted. Functional enrichment analysis of the candidate genes from genome-wide association study and integration analysis with our previous transcriptome data were conducted. The imputation accuracy parameters, allele frequency R² , concordance rate, and dosage R² were 0.959, 0.952, and 0.933, respectively. The heritability values of a*_45 min , b*_45 min , L*_45 min , C*, and H⁰ were 0.19, 0.11, 0.06, 0.16, and 0.26, respectively. In total, 3884 significant SNPs and 15 QTL, corresponding to 382 genes, were associated with meat color traits. Functional enrichment analysis revealed that 10 genes were the potential candidates for regulating meat color. Moreover, integration analysis revealed that DMRT2, EFNA5, FGF10, and COL11A2 were the most promising candidates affecting meat color. In summary, this study provides new insights into the molecular basis of meat color traits, and provides a new theoretical basis for the molecular breeding of meat color traits in pigs.

SNP discovery and association study for growth, fatness and meat quality traits in Iberian crossbred pigs

Iberian pigs and its crosses are produced to obtain high-quality meat products. The objective of this work was to evaluate a wide panel of DNA markers, selected by biological and functional criteria, for association with traits related to muscle growth, fatness, meat quality and metabolism. We used 18 crossbred Iberian pigs with divergent postnatal growth patterns for whole genome sequencing and SNP discovery, with over 13 million variants being detected. We selected 1023 missense SNPs located on annotated genes and showing different allele frequencies between pigs with makerdly different growth patterns. We complemented this panel with 192 candidate SNPs obtained from literature mining and from muscle RNAseq data. The selected markers were genotyped in 480 Iberian × Duroc pigs from a commercial population, in which phenotypes were obtained, and an association study was performed for the 1005 successfully genotyped SNPs showing segregation. The results confirmed the effects of several known SNPs in candidate genes (such as LEPR, ACACA, FTO, LIPE or SCD on fatness, growth and fatty acid composition) and also disclosed interesting effects of new SNPs in less known genes such as LRIG3, DENND1B, SOWAHB, EPHX1 or NFE2L2 affecting body weight, average daily gain and adiposity at different ages, or KRT10, NLE1, KCNH2 or AHNAK affecting fatness and FA composition. The results provide a valuable basis for future implementation of marker-assisted selection strategies in swine and contribute to a better understanding of the genetic architecture of relevant traits.

Understanding the role of myoglobin content in Iberian pigs fattened in an extensive system through analysis of the transcriptome profile

Meat color is the first perceived sensory feature and one of the most important quality traits. Myoglobin is the main pigment in meat, giving meat its characteristic cherry‐red color, highly appreciated by the consumers. In the current study, we used the RNA‐seq technique to characterize the longissimus dorsi muscle transcriptome in two groups of Iberian pigs with divergent breeding values for myoglobin content. As a result, we identified 57 differentially expressed genes and transcripts (DEGs). Moreover, we have validated the RNA‐seq expression of a set of genes by quantitative PCR (qPCR). Functional analyses revealed an enrichment of DEGs in biological processes related to oxidation (HBA1), lipid metabolism (ECH1, PLA2G10, PLD2), inflammation (CHST1, CD209, PLA2G10), and immune system (CD209, MX2, LGALS3, LGALS9). The upstream analysis showed a total of five transcriptional regulatory factors and eight master regulators that could moderate the expression of some DEGs, highlighting SPI1 and MAPK1, since they regulate the expression of DEGs involved in immune defense and inflammatory processes. Iberian pigs with high myoglobin content also showed higher expression of the HBA1 gene and both molecules, myoglobin and hemoglobin, have been described as having a protective effect against oxidative and inflammatory processes. Therefore, the HBA1 gene is a very promising candidate gene to harbor polymorphisms underlying myoglobin content, whereby further studies should be carried out for its potential use in an Iberian pig selection program.

Consequences of a low protein diet on the liver and longissimus dorsi transcriptome of Duroc × Iberian crossbred pigs

Low protein diets supplied during the growing period of pigs can diminish their growth rate and increase the intramuscular fat (IMF) content which affects the sensorial and technological characteristics of the products. In the present study, the effects of a low protein diet supplied during the growing period of Duroc × Iberian crossbred pigs on several phenotypic traits and on liver and longissimus dorsi transcriptome were analysed at the beginning (EARLY) and at the end (LATE) of the growing period. Two experimental groups of 10 crossbred pigs each were fed two isocaloric diets with different protein content: control diet (C) with 16.5% protein and 0.8% lysine and low protein diet (LP) with 11% CP and 0.6% lysine. Animals fed LP diet have a slower growth than those fed C diet, but no effect of LP diet was observed on the IMF content. The transcriptomes of liver and longissimus dorsi were characterised and quantified through RNA-sequencing (RNA-seq). In liver, 134 and 480 differentially expressed annotated genes and new isoforms (DEGs) were detected between C and LP diets for EARLY and LATE animals, respectively. In muscle, 128 and 68 DEGs were detected at EARLY and LATE time-points. Functional interpretation revealed that LP diet may inhibit immune system molecules and processes in both tissues at EARLY stage. In liver, the DEGs mainly affect lipid and cholesterol metabolic processes, while in muscle, the expression changes would be involved in growth, development and meat quality. In conclusion, a low protein diet supplied during the growing period seems to slow down the growth of Duroc × Iberian crossbred pigs, but it also seems to affect multiple biological processes that could compromise the immune system of Duroc × Iberian crossbred pigs. Therefore, these results question the adequacy of this type of regime in Duroc × Iberian pigs that must be studied in greater depth before being implemented.

Changes in Biceps femoris Transcriptome along Growth in Iberian Pigs Fed Different Energy Sources and Comparative Analysis with Duroc Breed

Simple Summary

The genetic mechanisms that regulate biological processes, such as skeletal muscle development and growth, or intramuscular fat deposition, have attracted great interest, given their impact on production traits and meat quality. In this sense, a comparison of the transcriptome of skeletal muscle between phenotypically different pig breeds, or along growth, could be useful to improve the understanding of the molecular processes underlying the differences in muscle metabolism and phenotypic traits, potentially driving the identification of causal genes, regulators and metabolic pathways involved in their variability.

Abstract

This experiment was conducted to investigate the effects of developmental stage, breed, and diet energy source on the genome-wide expression, meat quality traits, and tissue composition of biceps femoris muscle in growing pure Iberian and Duroc pigs. The study comprised 59 Iberian (IB) and 19 Duroc (DU) animals, who started the treatment at an average live weight (LW) of 19.9 kg. The animals were kept under identical management conditions and fed two diets with different energy sources (6% high oleic sunflower oil or carbohydrates). Twenty-nine IB animals were slaughtered after seven days of treatment at an average LW of 24.1 kg, and 30 IB animals plus all the DU animals were slaughtered after 47 days at an average LW of 50.7 kg. The main factors affecting the muscle transcriptome were age, with 1832 differentially expressed genes (DEGs), and breed (1055 DEGs), while the effect of diet on the transcriptome was very small. The results indicated transcriptome changes along time in Iberian animals, being especially related to growth and tissue development, extracellular matrix (ECM) composition, and cytoskeleton organization, with DEGs affecting relevant functions and biological pathways, such as myogenesis. The breed also affected functions related to muscle development and cytoskeleton organization, as well as functions related to solute transport and lipid and carbohydrate metabolism. Taking into account the results of the two main comparisons (age and breed effects), we can postulate that the Iberian breed is more precocious than the Duroc breed, regarding myogenesis and muscle development, in the studied growing stage.

Phenotypic and genetic correlations of pork myoglobin content with meat colour and other traits in an eight breed-crossed heterogeneous population

Meat colour is one of the most important meat quality traits affecting consumption desire. Genetic improvement for meat colour traits is not so easy because pigs can be phenotyped only after slaughter. Besides the parameters from the optical instrument, other indexes that reflect the material basis of meat colour should be measured accurately and used in the genomic analysis. Myoglobin (Mb) is the main chemical component determining meat colour. However, to what extent the Mb content contributes to meat colour, and whether it can be used as a trait for pig breeding to improve meat colour, and the correlations of Mb content with complex porcine traits are largely unknown. To address these questions, we measured the muscle Mb content in 624 pigs from the 7th generation of a specially designed eight breed-crossed pig heterogeneous population, evaluated its phenotypic and genetic correlations with longissimus thoracis colour score at 24 h after slaughter. More than that, we also systematically phenotyped more than 100 traits on these animals to evaluate the potential correlations between muscle Mb content and economically important traits. Our results showed that the average muscle Mb content in the 624 pigs was 1.00 mg/g, ranging from 0.51 to 2.17 mg/g. We found that higher Mb content usually correlated with favourable meat colour, higher marbling score, less moisture content, and less drip loss. Genetic correlation analysis between muscle Mb content and 101 traits measured in this study shows that Mb content is also significantly correlated with 31 traits, including marbling, shear force, firmness, and juiciness. To our knowledge, this is one of the largest studies about the correlations of muscle Mb content with as many as 100 various traits in a large-scale genetically diversified population. Our results showed that the Mb content could be a selection parameter for the genetic improvement of meat colour. The selection for higher Mb content will also benefit marbling, shear force, firmness, and overall liking but might not affect the growth, carcass, and fat deposition traits.

RNA Profiles of the Korat Chicken Breast Muscle with Increased Carnosine Content Produced through Dietary Supplementation with β-Alanine or L-Histidine

Simple Summary

Carnosine is a bioactive food component with several potential health benefits for humans due to its physiological functions. Dietary supplementation with β-alanine or L-histidine can increase the carnosine content of skeletal muscles in chickens. Dietary supplementation with β-alanine or L-histidine has produced a slow-growing chicken variety with high carnosine content in the breast meat; however, the supplementation with L-histidine alone softens the meat toughness, which may affect consumers’ willingness to buy the meat. Gene expression is a key factor that influences meat quality. Understanding the molecular mechanisms that affect carnosine content and meat toughness would allow the production of more value-added slow-growing chickens. We compared global gene expression in chicken breast muscles with differing carnosine contents and meat toughness produced through dietary supplementation with β-alanine or L-histidine. We identified differentially expressed genes involved in regulating myosin, collagen, intramuscular fat, and calpain—factors that may affect meat tenderness. Pathway enrichment analysis indicated that the insulin-related and adipocytokine signaling pathways were altered by dietary supplementation with β-alanine or L-histidine. These data will be useful for future studies on carnosine content and meat toughness in slow-growing chickens.

Abstract

Korat chicken (KRC) is a slow-growing chicken bred in Thailand, whose meat exhibits a unique toughness. A previous study produced KRC breast meat containing high carnosine content through dietary supplementation with β-alanine or L-histidine; however, the KRC that were fed an L-histidine-supplemented diet produced meat that was significantly more tender. Herein, we performed RNA-Seq to identify candidate genes involved in the regulation of carnosine content and meat toughness. Total RNA was isolated from five female KRC breast muscles in each treatment group that KRC fed diets without supplementation, supplemented with β-alanine or L-histidine. Compared to the non-supplemented group, we identified 118 and 198 differentially expressed genes (DEGs) in the β-alanine or L-histidine supplementation groups, respectively. Genes potentially related to meat tenderness—i.e., those regulating myosin, collagen, intramuscular fat, and calpain—were upregulated (LOC107051274, ACSBG1, and CAPNS2) and downregulated (MYO7B, MYBPH, SERPINH1, and PGAM1). However, carnosine synthase gene was not identified. Functional enrichment analysis identified pathways affected by dietary supplementation, including the insulin signaling pathway (β-alanine supplementation) and the insulin resistance and adipocytokine signaling pathways (L-histidine supplementation). The FoxO signaling pathway was identified as a regulatory network for both supplementation groups. The identified genes can be used as molecular markers of meat tenderness in slow-growing chickens.

Differences in the Loin Tenderness of Iberian Pigs Explained through Dissimilarities in Their Transcriptome Expression Profile

Simple Summary

The Iberian pig is the most representative autochthonous breed of the Mediterranean region with unique genetic and phenotypic characteristics. The breed has been successfully preserved by its high-quality meat and high-priced products. Tenderness is one of the most relevant meat quality traits, and meat tenderization is influenced by genetic and environmental effects such as pre-slaughter handling and post-mortem conditions. Tenderness could be included in Iberian pig breeding programs, mainly focused on the improvement of premium-cuts percentage, in order to avoid the meat quality decline. A better biological understanding of this trait is needed. In the current study, we analyze the transcriptome of pigs divergent for Warner–Bratzler shear force through RNA-seq technique for the identification, characterization and quantification of candidate genes involved in biological pathways, networks and functions affecting meat tenderness.

Abstract

Tenderness is one of the most important meat quality traits and it can be measured through shear force with the Warner–Bratzler test. In the current study, we use the RNA-seq technique to analyze the transcriptome of Longissimus dorsi (LD) muscle in two groups of Iberian pigs (Tough and Tender) divergent for shear force breeding values. We identified 200 annotated differentially expressed genes (DEGs) and 245 newly predicted isoforms. The RNAseq expression results of 10 genes were validated with quantitative PCR (qPCR). Functional analyses showed an enrichment of DE genes in biological processes related to proteolysis (CTSC, RHOD, MYH8, ACTC1, GADD45B, CASQ2, CHRNA9 and ANKRD1), skeletal muscle tissue development (ANKRD1, DMD, FOS and MSTN), lipid metabolism (FABP3 and PPARGC1A) and collagen metabolism (COL14A1). The upstream analysis revealed a total of 11 transcription regulatory factors that could regulate the expression of some DEGs. Among them, IGF1, VGLL3 and PPARG can be highlighted since they regulate the expression of genes involved in biological pathways that could affect tenderness. The experiment revealed a set of candidate genes and regulatory factors suggestive to search polymorphisms that could be incorporated in a breeding program for improving meat tenderness.